Internal geneva lock



Nov. '18, 1969 F. E. SMITH 3,478,616

INTERNAL GENEVA LOCK Filed May 22, 1968 s Sheets-Sheet 1 INVENTOR FLOYD E. SMITH AT TYS.

Tllillllllllllr Ill. 28 I Nov. 18, 1969 F. E. SMITH 3,478,616

INTERNAL GENEVA LOCK Filed May 22, 1968 3 Sheets-Sheet 2 VENTOR FLO E. SMITH ATTYS.

Nov. '18, 1969 F. E. SMITH 1 3,478,616

INTERNAL GENEVA LOCK Filed May 22, 1968 3 Sheets-Sheet 5 INVENTOR FLOYD E. SMITH AT-TYS.

United States Patent M INTERNAL GENEVA LOCK Floyd E. Smith, 5704 Brewster Lane, Erie, Pa. 16505 Filed May 22, 1968, Ser. No. 731,211 Int. Cl. F16h 55/04 US. Cl. 74-436 9 Claims ABSTRACT OF THE DISCLOSURE Internal four station and eight station Genevas in which arcuate relief is provided on the Geneva wheel to accommodate design capability of 180 lockup with the locking segment on the Geneva driver. Additional means disengage the driving power at a mid-point in the dwell position and in timed relationship to shift the driver to the end that a zero tolerance lockup can be provided at the mid-point in the dwell to thereby maximize the radial accuracy of alignment of a work table driven by the Geneva wheel.

The present invention relates to a Geneva lock, and more particularly a design of an internal Geneva which permits the moving parts to achieve a lock-up at the median portion and dwell far more accurately than that available with conventional internal Genevas.

For years, external Genevas have been used in providing intermittent rotational motion. Basically as the number of stations decrease on an external Geneva, acceleration for a given drive or radial speed increases. For example, with a four station external Geneva, 270 of the rotation of the driver is devoted to dwell, whereas 90 is devoted to rotation. Thus one-quarter of a rotation of the driver rotates the Geneva one-quarter of its rotational distance. On the other hand an eight station external Geneva provides 135 of dwell, and 225 of drive. Thus, as the number of stations increase with an external Geneva, the acceleration during indexing is less pronounced than with the four station unit. In operation, particularly with the trend toward 60 indexes per minute, and indeed present goals of 100 indexes per minute, knocking can be experienced with the four station externals because of the substantial acceleration which, when coupled to a work table with parts providing initial inertia, can result in undersirable pounding.

Looking to the features of the internal Geneva, as the number of stations decrease, the acceleration for a given driver radial speed decreases. Accordingly, one would assume that to eliminate pounding, one should resort to an internal Geneva and therefore employ a four station internal. With a four station internal Geneva, however, 270 of the rotation of the driver is devoted to indexing, and 90 for dwell. This result is the exact opp'osite'of a four station external. With a four station external the 270 of dwell permits accuracy in orientation during the dwell period attributable to the long arcuate contact between the driver arcuate members and the arcuate mating lockup portions of the Geneva. With a four station internal Geneva, however, the arcuate portion of the driver available for effective contact with the arcuate portion of the Geneva is less than 180, actually only 90 with the conventional internal four station. Quite obviously, therefore, in the four station internal where one is seeking to obtain positive orientation during the dwell cycle, the possibility of opposed arcuate face-to-face contact between the driver and the Geneva is held to a minimum if not eliminated.

The present invention stems from the discovery that by relieving the mid-portion of the Geneva locking arc, 180 of lock, at the median position of the driver, is a design possibility in a low-numbered station internal Geneva. More specifically, 180 of lockup can be achieved with a four station, six station, or eight station internal Geneva by employing relief in the arcuate face of the Geneva locking portion between the cam follower slots as will be set forth in detail hereinafter. Additionally, the same relief may be employed in an external Geneva to reduce the phenomenon known as ratcheting.

With the prior art type internal Geneva lockup, the arcuate face on the driver is limited by perpendicular cutoffs from the adjacent axes of the driver slots with the arc radius being tangential to the slots. As set forth above, 180 lockup cannot in theory be achieved with such an internal design without providing relief somewhere.

By relieving the mid-portion of the Geneva arc, however, 180 of lockup can be achieved with all internal Genevas of common usage, that is, between four and sixteen, on even multiples, or odd, if specials of this character are desired. The relief is centered on the concave locking are on an arc approximating the angular displacement of the slots. Thus with a four station Geneva, the angular displacement of the cam follower slots being 90, approximately 90 of relief is provided at a mid-portion in the concave arcuate locking face on the Geneva wheel. With an eight station internal, where the spacing arcuately between the adjacent cam follower slots is 45", approximately 45 of relief is provided centrally on the arcuate lock face between the adjacent slots.

The present invention will be more fully understood as the following description of an illustrative embodiment proceeds, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective partially broken and partially diagrammatic view showing an internal Geneva illustrative of the present invention employed in driving an indexing table which desirably would be employed in an automated four station operation.

FIG. 2 is a plan view of the four station Geneva wheel illustrative of the present invention.

FIG. 3 at the upper portion shows a plan view of the four station Geneva driver and locking segment with cam follower, and at the lower portion shows an end view of the same illustrating the orientation of the drive shaft and drive shaft hub.

FIGS. 4 through 16 inclusive are sequential views illustrating the dynamic relationship between the illustrative driver and Geneva showing particularly in FIG. 4 how 180 of lockup is achieved, in FIGS. 7 through 9 inclusive how the relief on the Geneva arcuate portion permits the same.

FIG. 17 is a plan view of an eight station internal Geneva illustrating the full lock feature of the present invention.

FIG. 18 is a plan view of a driver proportioned for use with the eight station shown in FIG. 17.

FIG. 19 is an enlarged partially broken partially diagrammatic view illustrating the center line relationship between two adjacent cam follower slots in a four station internal Geneva showing in phantom line relationship the difference between the prior art lockup and the full lock achieved by a structure illustrative of the present invention.

FIG. 20 is a view similar to FIG. 19 except showing the relationship between adjacent cam follower slots in an eight station Geneva.

FIG. 21 shows in plan view how the arcuate relief illustrative of the invention may be employed with an external Geneva.

Referring now to FIG. 1, it will be seen that a typical indexing table or work table 11 is disclosed in an internal Geneva drive assembly 10. The work table is shown as mounted for support in a ring bearing 12 which is Patented Nov. 18, 1969 i secured to an external structure which would house work stations for performing four operations on a work piece to be indexed with the four station internal Geneva disclosed. The housing 14 is provided for the motor 16, and sets atop a mounting plate 15 which is secured to a work table or the host equipment.

The motor 16 shown here as an electric type is coupled by means of a drive shaft 18 to a gear box 19 which contains a bevel reduction gear. It will be appreciated that while a 90 bevel gear has been shown in this instance, the same will function with a worm screw as the output for the electric motor, and a worm gear mounted beneath the Geneva driver. A drive shaft 20 for the Geneva driver extends upwardly from the gear box 19 and operates the Geneva driver 25. As illustrated, a spline on the motor drive shaft 18, and a gib type slide 22 secures the gear box to the mounting plate 15, the gear box 19 being actuated along the axis of the slide 22 by means of the lock cylinder 23. The purpose of the aforesaid structure including the lock cylinder 23 will be set forth in detail hereinafter, but for present purposes its principal function is to translate the Geneva drive 25 into a zero clearance mid-position lock to thereby secure the work table 11 at a mid-point in the dwell of the Geneva operation locked for the performing of an assembly function at one of the work stations.

Referring now to FIGS. 3 and 4, the coordinated relationship between the Geneva driver 25 and the Geneva wheel 40 will be better understood. In FIG. 3 at the upper portion a plan view of the Geneva driver 25 is shown where it will be observed that a drive plate portion 26 serves to connect the driver cam follower 28 in operative relationship to the locking segment 30. In the end view shown at the bottom portion of FIG. 3 it will be seen that the drive shaft of the Geneva driver 20 is secured to a drive shaft hub 29 at the bottom of the drive plate 26. Referring again to the upper portion in FIG. 3, it will be seen that the locking segment 30 has locking segment ends 31 which are 180 opposed to each other and diametrically opposed, defining therebetween arcuate locking faces 32. It will be noted that a locking face relief has been optionally shown by dotted lines which can serve the twofold purpose of reducing weight, and providing for additional clearance in certain conditions, although when manufactured to precise tolerances, the locking face relief does not appear to be essential in normal internal Geneva designs from four to sixteen stations. For convenience of reference the numeral 35 has been employed to define the driver axis which is the center of the Geneva driver drive shaft 20 as shown in the 7 bottom portion of FIG. 3.

Referring now to FIG. 2, it will be seen that the Geneva wheel 40, a four station Geneva wheel, employs four cam follower slots 41 which are oriented on 90 spacing. Concave lock arcs 42 are defined between the cam follower slots 41 and terminate in slot ends 44. As will be observed, the driver axis or center 35 is positioned at a center point along the median dwell center line 50, and the variables such as the center distance between the driver axis 35 and the Geneva axis 48, slot width, and driver locking radius determines the width of the slot ends 44. In practice it has been found desirable to proportion the aforementioned design variables so that the ends 44 are at least across, and preferably In operations where large loads are not involved, and rotational speeds are slow, this end dimension of the ends 44 is not as critical as when either high speeds or substantial loads are involved thereby dictating the design criteria set forth above.

In order to achieve the 180 orientation of the locking segment ends 31 shown in FIG. 3, and provide sufiicient clearance for rotation, a relief 45 is provided in arcuate form for the driver segment ends at a mid-portion between the concave lock arc 42 in the Geneva between its drive slots 41. It has been observed that there is a relationship between the arcuate dimensions of the relief and the arcuate relationship of the drive slots 41; namely, that the arc A shown as identical in both instances in FIG. 2, must be equaled or exceeded when determining the arcuate relief 45 for the driver segment ends.

By referring now to FIGS. 4 through 16 in sequence, the operation of the four stations shown in FIGS. 2 and 3 will be better understood. For purposes of explanation, a locking face relief 34 has been shown on the locking segment 30 of the driver 25, but here again it should be pointed out that the provision of this relief is optional, and with good design to close tolerances is not necessary in four, eight, and sixteen station internal Genevas to provide the function of 180 arcuate locking at the mid-point of the dwell. The dwell mid-point position is shown in FIG. 4 where it will be observed by the center line that the ends 31 of the locking segment 30 are in 180 opposed relationship and secured against the concave lock arcs 42 of the Geneva wheel '40. The driver cam follower 28 is at its mid-position between the Geneva wheel cam follower slots 41. It is at this point where shifting the axis 35 of the driver radially outward from the center of the Geneva 48 as shown by the arrow pointing upwardly passing through the driver axis 35, achieves a no clearance situation at the interspace between the concave lock arcs 42 of the Geneva wheel 40 and the arcuate locking faces 32 of the locking segment 30. As pointed out in connection with the description of FIG. 1, this action may be achieved by actuating the lock cylinder 23 in timed relationship to the mid-dwell position of the cam follower 28 through its lock shaft 24 to the gear box 19 which is shifted slightly by the action of the lock cylinder 23. At this point it should be remarked that de-clutching the motor drive shaft 18 by means of a clutch on the drive shaft, or on the Geneva driver drive shaft 20, or within the gear box 19 is essential. Therefore the entire action of translating the axis 35 of the driver, de-clutching the motor 16 should be substantially simultaneous and sensed to occur in substantially simultaneous timed relationship to the end that the 180 locking relationship is achieved between the arcuate locking faces 32 of the driver and the concave lock arc faces 42 of the Geneva wheel 40. The dwell in this locked relationship, because of the 180' opposed relationship of the locking segment ends 31 of the driver, spreads any inaccuracies in the look over the furtherest possible distance from the median dwell center line 50 thereby holding arcuate inaccuracies to an irreducible minimum. Furthermore, in the prior art, shot pins, V-blocks, and the like are employed to engage the work table 11 to secure such radial accuracy, Whereas by employing the structure of the present invention with the arcuate relief 45 on the Geneva, the same action can be insured with the dynamic operation of the Geneva wheel itself without resort to external orientation techniques which in and of themselves can introduce inaccuracies radially, because their orientation is not taken from the Geneva drive itself.

An alternative intermittent lock is achieved when the driver and wheel lock radii 32, 42 are formed for a frustoconical fit and the drive shaft 20 shift it along its axis.

Referring to FIG. 2, the circle which is dictated by the portions of the lock radius 42 is formed with a frustoconical face so that the circular portion appearing on the top of the plate in FIG. 2 is smaller than the diameter on the bottom of the plate. Thus the circle determined by the portions of lock radius 32 being of a smaller diameter at the top than the bottom, when the driver member 26 is movedvertically by shifting the drive shaft 20, an interference or clearance closure between the conical portions of the lock radius 32 and 42 occur. While in effect the action is comparable to that of a shot pin, intermittent locking of the Geneva occurs, and the action of shifting the drive shaft 20 simultaneous declutches the drive. Additionally, the diameter of the locking radius 32 on the driver can be expanded in the manner of a brake shoe,

or chuck to the end that intermittent zero backlash locking may be provided.

Returning now to FIGS. 4 through 16 inclusive, it will be seen in FIG. 5 that the driver 35 is now beginning to rotate in counter-clockwise direction, the'clutch having been re-engaged in the axis of rotation of the driver 25 shifted to its normal position. The arcuate lockup between the driver locking faces 32 and the Geneva locking concave arc 42 still remains intact.

In the condition beginning as shown in FIG. 6, however, the locking segment ends 31 of the locking segment 30 of the driver 25 moves imperceptibly into the locking face relief 34 in the Geneva wheel. This condition is progressively illustrated in FIG. 7 where it will be clearly seen that the relief 34 accommodates the end 31 of the locking segment. Were the relief 34 not present, the design of the arc which would lirnit the locking segment 30 to approximately 90 would be required to permit operation without metallic interference. Asthe cam follower 28 proceeds further to engage the cam follower slot 41 as shown in FIG. 8, it will be noticed that the left hand concave lock are 42 of the Geneva wheel 40 has moved sufiiciently far away that the optionally shown locking face relief 34 clearly is not indicated. Indeed, upon review of the operation from FIGS. '4 through 8, it will be noticed that the left hand concave lock are 42 of the Geneva wheel 40 has moved sufiiciently far away'that the optionally shown locking face relief 34 clearly is not indicated. Indeed, upon review of the operation from FIGS. 4 through 8, it will be seen that where'preciSe tolerances are the subject of design, this locking face relief 34 is unnecessary. Thus, where substantially heavy loads are involved, and high speeds, it is more desirable to eliminate the locking face relief 34 in order to have a full 180 of arcuate contact to absorb the inertia backing when the cam follower 28 emerges from the cam follower slot 41 in the conditions illustrated in FIGS. and 16.

As observed in FIG. 9, the maximum relief 34 is required at the mid-point in the travel of the cam follower 28 onto the cam follower slot 41. Proceeding on to FIG. 10, it will be seen that as the cam follower 28 approaches the end of the cam follower slot 41 the locking segment 30 of the Geneva driver 25 is substantially free of contact with any metallic elements. Thereafter, as the cam follower 28 approaches the far end of the cam follower slot 41 in the conditions shown progressively in FIGS. 11 and 12, the Geneva slot end clearance arc 36 of the locking segment 30 becomes significant. The condition shown as the cam follower 28 begins emerging from the cam follower slot 41 progressively illustrated in FIGS. 13 through 15 requires no different design clearances than those shown in FIGS. 7 through 11 inclusive as the cam fallower 28 is entering the cam follower slot 41. As a result, the design configuration of the locking segment 30 is one of mirror image relationship, or bilateral symmetry about the axis defined by the center of the driver cam follower 28 is entering the cam follower slot 41. As a 16, immediately at the departure of the cam follower 28 from the arcuate slot 41 to the beginning of the dwell cycle, the ends 31 of the locking segment 30 begin their arcuate contact with the concave lock are 42 of the Geneva wheel 40, and this condition continues and augments itself until the mid-point of dwell is achieved in the condition shown in FIG. 4.

While the description has been specifically related to a four station internal Geneva, it will be observed in FIGS. 17 and 18 that an eight station internal Geneva is susceptible of the same type of design, the difference lying primarily in the 45 included angle defined between the adjacent cam follower slots 41. Identical reference numerals are used on the eight station Geneva illustrating its comparable employment of the principles set forth in the four station description. While the 180 relationship with the locking segment 30 can still be preserved in the eight station Geneva, the improvement over the prior art is less pronounced inasmuch as without the arcuate relief 45 for the driver segment ends as provided, conventional type internal Genevas can provide of locking arc, rather than only 90 as with a four station internal of the prior art. Reference to FIGS. 19 and 20 which show respectively the specific centers and orientation of the driver and Geneva wheel of four stations and eight stations illustrates more graphically the relationship between the prior art lockup and the lockup which can be achieved by following illustrations of the present invention and providing arcuate relief for the driver segment ends. The arcuate locking face extension 33 from the prior art is shaded for emphasis in FIGS. 3, 18, 19 and 20.

In operation, while the specific details of the clutch and axis shifting mechanism have not been shown, it will be appreciatedthat the cam follower is the ideal sensing device, and indeed driving device, for the clutch to disengage the power source from the Geneva driver drive shaft 20 and also shift the driver axis 35 radially voutwardly to insure positive lockup. In the structure shown in FIG. 1, the lock cylinder 23 is engaged and actuated by means of a micro-switch (not shown) which takes its intelligence from the driver cam follower 28, and upon shifting the gear box 19, clutch means disengage the motor drive shaft 18.

Also as set forth above, similar expedients are available for shifting the driver wheel drive shaft 20 axially when conical interfaces are employed on the driver concave lock arc 42 and mating arcuate locking faces 32. As indicated in the objects, certain advantages occur when the arcuate relief 45 is applied to an external Geneva to permit a larger radius of lockup, and thus reduce the phenomenon of ratcheting.

In review, it will be seen that an illustrative four station and eight station internal Geneva has been disclosed and described in which of lockup can be achieved. The means for achieving the lockup is attributable to the employment of relief in an arcuate form of the Geneva wheel intermediate the ends of the concave locking arcs which, in turn, are adjacent the ends of the cam follower slots. As set forth, the arcuate dimension of the relief 45 as shown and described in the four station and eight station must be not less than the radial spacing of adjacent cam follower slots. This relationship holds true for any number of stations between four and sixteen. With more than sixteen stations, Genevas of the present design are relatively infrequently employed in industry, and the same is true for less than four stations. Indeed, the four station is one of the most popular, and it has been the principal object of the present invention to provide 180 of locking action at the mid-point on the dwell in a four station internal. The result achieved is to harness the desirable acceleration curve of a four station internal, and yet provide the radial orientation accuracy of a four station external.

Although particular embodiments of the invention have been shown and described in full here, there is no intention to thereby limit the invention to the details of such embodiments. On the contrary, the intention is to cover all modifications, alternative embodiments, usages and equivalents of an internal Geneva lock as fall within the spirit and scope of the invention.

What is claimed is:

1. An internal Geneva comprising, in combination, a driver mounted for rotation, said driver having a cam follower and an arcuate locking face having ends in diametrically opposed orientation on the driver with respect to the axis of rotation of the driver; and a Geneva wheel, said wheel having cam follower slots oriented radially from the Geneva wheel center, concave lock arcs intermediate the cam follower slots on the Geneva wheel, each said lock are having at a mid-point therebetween arcuate relief means of angular dimension sufiicient to clear the ends of the driver arcuate locking face ends thereby insuring a design capability of 180 of arcuate contact between the driver arcnate lock and the Geneva concave lock arcs at the dwell median position.

2. In the internal Geneva of claim 1, arcuate relief means of angular dimension not less than the radial spacing of the cam follower drive slots.

3. In the internal Geneva of claim 1, means for yieldably shifting the axis of rotation of the driver outwardly from the center of the Geneva wheel along a radial of the Geneva midway between two adjacent slots.

4. In the Geneva of claim 3, said means comprising a drive shaft for the drive Wheel, and yieldable means secured to the drive shaft for shifting the same toward an axis outward radially with respect to the Geneva thereby yieldably eliminating the clearance between driver arcuate locking faces and the concave Geneva lock arcs.

5. In the Geneva of claim 3, clutch means for disengaging the drive in timed relation to the shifting of the axis of drive rotation.

6. In the Geneva of claim 5, means actuated by the drive cam to clutch and shift in timed relation thereby locking the Geneva at its dwell mid-point.

7. In the Geneva of claim 1, clutch means for disengaging the drive in timed relation to its mid-point dwell position.

8. In the Geneva of claim 1, means actuated by the drive cam follower for disengaging the drive at the midpoint of the dwell.

9. In the Geneva of claim 8, means actuated by the drive cam to clutch and shift in timed relation thereby locking the Geneva at its dwell mid-point.

References Cited UNITED STATES PATENTS 632,906 9/1899 SWasey 74820 3,153,952 10/1964 Thoma 74-436X LEONARD H. GERIN, Primary Examiner 

